Sudden limb weakness in the elderly is generally divided into two cases: 1, caused by diseases of the nervous system, a common disease called Guillain-Barré syndrome, which is often caused by autoimmune reactions, the site of onset is the nerve root of the spinal nerve. This disease is often caused by autoimmune reactions to the nerve roots of the spinal nerve. Due to the autoimmune response, a rejection reaction occurs to the components of the nerve root myelin sheath, resulting in the loss of the nerve root myelin sheath and the destruction of the nerve fibers, resulting in sudden weakness of the limbs. sudden weakness of the limbs in the elderly.